remctl 2.4

The big change in this version is IPv6 support, using the framework and
infrastructure that I'd built for INN. I'm really happy with how well this
works. It keeps all the problems self-contained in the portability layer
and the code can use the new IPv6-aware interfaces like getaddrinfo and
getnameinfo without having to think about IPv6 issues.

I also fixed a problem with detecting network errors when sending tokens,
added a newline after server-provided error messages in the command-line
client, and added a distinguished error for too many command-line
parameters.